3-Indolepropionic acid

3-Indolepropionic acid (IPA), or indole-3-propionic acid, has been studied for its therapeutic value in the treatment of Alzheimer's disease. As of 2022 IPA shows potential in the treatment of this disease, though the therapeutic effect of IPA depends on dose and time of therapy initiation.

Though promising in some historical clinical trials, IPA is not clinically listed as a useful therapeutic in managing Alzheimer's as of 2023.

This compound endogenously produced by human microbiota and has only been detected in vivo when the species Clostridium sporogenes is present in the gastrointestinal tract. , C. sporogenes, which uses tryptophan to synthesize IPA, is the only species of bacteria known to synthesize IPA in vivo at levels which are subsequently detectable in the blood plasma of the host.

IPA is an even more potent scavenger of hydroxyl radicals than melatonin, the most potent scavenger of hydroxyl radicals that is synthesized by human enzymes. Similar to melatonin but unlike other antioxidants, it scavenges radicals without subsequently generating reactive and pro-oxidant intermediate compounds. In 2017, elevated concentrations of IPA in human blood plasma were found to be correlated with a lower risk of type 2 diabetes and higher consumption of fiber-rich foods.

Metabolism
IPA can be converted in the liver or kidneys to 3-indoleacrylic acid, which is subsequently conjugated with glycine, forming indolylacryloyl glycine.

History
The neuroprotective, antioxidant, and anti-amyloid properties of IPA were first reported in 1999.